# match a line that only contains one new line
if ($line =~ /^\n$/) {

##</code><code>##

# match a line that only contains one or more whitespace
if ($line =~ /^\s+$/) {

##</code><code>##

foreach (@blah) {
   if ($foo) {
      # foo stuff
   }
   else {
      # other stuff
   }
}

##</code><code>##

# open filehandles ...

my ($s, $b) = (0,0);
my $arc     = 'ARCSERVE.NLM'; 
my @lines   = <DATA>;

foreach my $line (@lines) {
	if ($line =~ /^\s+$/ and $s) {
		$b++;
		last if $b == 2;
	}
	$s = 1 if $line =~ /$arc/;

	print OUTPUT $line if $s and $line !~ /^\s+$/;
}